title: Spin-valley lifetimes in a silicon quantum dot with tunable valley splitting.
abstract: Although silicon is a promising material for quantum computation, the degeneracy of the conduction band minima (valleys) must be lifted with a splitting sufficient to ensure the formation of well-defined and long-lived spin qubits. Here we demonstrate that valley separation can be accurately tuned via electrostatic gate control in a metal-oxide-semiconductor quantum dot, providing splittings spanning 0.3-0.8 meV. The splitting varies linearly with applied electric field, with a ratio in agreement with atomistic tight-binding predictions. We demonstrate single-shot spin read-out and measure the spin relaxation for different valley configurations and dot occupancies, finding one-electron lifetimes exceeding 2 s. Spin relaxation occurs via phonon emission due to spin-orbit coupling between the valley states, a process not previously anticipated for silicon quantum dots. An analytical theory describes the magnetic field dependence of the relaxation rate, including the presence of a dramatic rate enhancement (or hot-spot) when Zeeman and valley splittings coincide.
authors.affiliation: Australian Research Council Centre of Excellence for Quantum Computation and Communication Technology, School of Electrical Engineering & Telecommunications, The University of New South Wales, Sydney 2052, Australia.
authors.forename: C H
authors.initials: CH
authors.lastname: Yang
authors.forename: A
authors.initials: A
authors.lastname: Rossi
authors.forename: R
authors.initials: R
authors.lastname: Ruskov
authors.forename: N S
authors.initials: NS
authors.lastname: Lai
authors.forename: F A
authors.initials: FA
authors.lastname: Mohiyaddin
authors.forename: S
authors.initials: S
authors.lastname: Lee
authors.forename: C
authors.initials: C
authors.lastname: Tahan
authors.forename: G
authors.initials: G
authors.lastname: Klimeck
authors.forename: A
authors.initials: A
authors.lastname: Morello
authors.forename: A S
authors.initials: AS
authors.lastname: Dzurak